Supervisory control

In the other, the process accepts an instruction, carries it out autonomously, reports the results and awaits further commands.

This concept was incorporated in the earliest machines which sought to extend the physical capabilities of man.

In contrast, with automatic control, the machine adapts to changing circumstances and makes decisions in pursuit of some goal which can be as simple as switching a heating system on and off to maintain a room temperature within a specified range.

Automatic control requires sensing and responding appropriately to all combinations of circumstances which can present problems of overwhelming complexity.

All time critical feedback occurs at the slave where the delays are negligible.